@@ -358,7 +358,7 @@ struct tcp_sock {
*/
int lost_cnt_hint;
- int retransmit_cnt_hint;
+ u32 retransmit_high; /* L-bits may be on up to this seqno */
u32 lost_retrans_low; /* Sent seq after any rxmit (lowest) */
@@ -472,6 +472,8 @@ extern void tcp_send_delayed_ack(struct sock *sk);
/* tcp_input.c */
extern void tcp_cwnd_application_limited(struct sock *sk);
+extern void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp,
+ struct sk_buff *skb);
/* tcp_timer.c */
extern void tcp_init_xmit_timers(struct sock *);
@@ -979,17 +979,17 @@ static void tcp_update_reordering(struct sock *sk, const int metric,
}
}
-/* RFC: This is from the original, I doubt that this is necessary at all:
- * clear xmit_retrans hint if seq of this skb is beyond hint. How could we
- * retransmitted past LOST markings in the first place? I'm not fully sure
- * about undo and end of connection cases, which can cause R without L?
- */
+/* This must be called before lost_out is incremented */
static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
{
- if ((tp->retransmit_skb_hint != NULL) &&
+ if ((tp->retransmit_skb_hint == NULL) ||
before(TCP_SKB_CB(skb)->seq,
TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
- tp->retransmit_skb_hint = NULL;
+ tp->retransmit_skb_hint = skb;
+
+ if (!tp->lost_out ||
+ after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high))
+ tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
}
static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
@@ -1002,6 +1002,16 @@ static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
}
}
+void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb)
+{
+ tcp_verify_retransmit_hint(tp, skb);
+
+ if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
+ tp->lost_out += tcp_skb_pcount(skb);
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ }
+}
+
/* This procedure tags the retransmission queue when SACKs arrive.
*
* We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
@@ -1178,13 +1188,7 @@ static void tcp_mark_lost_retrans(struct sock *sk)
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
tp->retrans_out -= tcp_skb_pcount(skb);
- /* clear lost hint */
- tp->retransmit_skb_hint = NULL;
-
- if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
- tp->lost_out += tcp_skb_pcount(skb);
- TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
- }
+ tcp_skb_mark_lost_uncond_verify(tp, skb);
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);
} else {
if (before(ack_seq, new_low_seq))
@@ -1890,6 +1894,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
tp->lost_out += tcp_skb_pcount(skb);
+ tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
}
}
tcp_verify_left_out(tp);
@@ -1974,6 +1979,7 @@ void tcp_enter_loss(struct sock *sk, int how)
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
tp->lost_out += tcp_skb_pcount(skb);
+ tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
}
}
tcp_verify_left_out(tp);
@@ -1836,7 +1836,7 @@ void tcp_simple_retransmit(struct sock *sk)
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *skb;
unsigned int mss = tcp_current_mss(sk, 0);
- int lost = 0;
+ u32 prior_lost = tp->lost_out;
tcp_for_write_queue(skb, sk) {
if (skb == tcp_send_head(sk))
@@ -1847,17 +1847,13 @@ void tcp_simple_retransmit(struct sock *sk)
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
tp->retrans_out -= tcp_skb_pcount(skb);
}
- if (!(TCP_SKB_CB(skb)->sacked & TCPCB_LOST)) {
- TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
- tp->lost_out += tcp_skb_pcount(skb);
- lost = 1;
- }
+ tcp_skb_mark_lost_uncond_verify(tp, skb);
}
}
tcp_clear_all_retrans_hints(tp);
- if (!lost)
+ if (prior_lost == tp->lost_out)
return;
if (tcp_is_reno(tp))
@@ -2007,15 +2003,11 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
const struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *skb;
- int packet_cnt;
- if (tp->retransmit_skb_hint) {
+ if (tp->retransmit_skb_hint)
skb = tp->retransmit_skb_hint;
- packet_cnt = tp->retransmit_cnt_hint;
- } else {
+ else
skb = tcp_write_queue_head(sk);
- packet_cnt = 0;
- }
/* First pass: retransmit lost packets. */
if (tp->lost_out) {
@@ -2026,7 +2018,6 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
break;
/* we could do better than to assign each time */
tp->retransmit_skb_hint = skb;
- tp->retransmit_cnt_hint = packet_cnt;
/* Assume this retransmit will generate
* only one packet for congestion window
@@ -2037,6 +2028,8 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
*/
if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
return;
+ if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high))
+ break;
if (sacked & TCPCB_LOST) {
if (!(sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) {
@@ -2057,10 +2050,6 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
inet_csk(sk)->icsk_rto,
TCP_RTO_MAX);
}
-
- packet_cnt += tcp_skb_pcount(skb);
- if (packet_cnt >= tp->lost_out)
- break;
}
}
}
Main benefit in this is that we can then freely point the retransmit_skb_hint to anywhere we want to because there's no longer need to know what would be the count changes involve, and since this is really used only as a terminator, unnecessary work is one time walk at most, and if some retransmissions are necessary after that point later on, the walk is not full waste of time anyway. Since retransmit_high must be kept valid, all lost markers must ensure that. Now I also have learned how those "holes" in the rexmittable skbs can appear, mtu probe does them. So I removed the misleading comment as well. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> --- include/linux/tcp.h | 2 +- include/net/tcp.h | 2 ++ net/ipv4/tcp_input.c | 34 ++++++++++++++++++++-------------- net/ipv4/tcp_output.c | 25 +++++++------------------ 4 files changed, 30 insertions(+), 33 deletions(-)